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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>

</body>
<script>
    // classList  =>  add  remove replace contains toggle
    
    // clientWidth  clientHeight
    // scrollWidth  scrollHeight
    // scrollLeft   scrollTop

    // offsetLeft   offsetTop  (offsetParent)

    // 伪数组    Array.from
    
    // let const 


</script>

</html>